There are many reasons we would be wrong in these expectations, however. First, the electorate isn’t entirely stable. Each generation of voters has been a bit different from the last. Over time, the United States has become more socially liberal, especially on topics related to race and gender, and millennials—those aged 18–34—are more liberal than members of older generations.

The electorate’s economic preferences have changed, and different social groups are likely to become more engaged in politics now than they did in the past. Surveys conducted in 2016, for example, revealed that candidates’ religion is less important to voters than it once was. Also, as young Latinos reach voting age, they seem more inclined to vote than do their parents, which may raise the traditionally low voting rates among this ethnic group.

Internal population shifts and displacements have also occurred, as various regions have taken their turn experiencing economic growth or stagnation, and as new waves of immigrants have come to U.S. shores.

Additionally, the major parties have not always been unified in their approach to contesting elections. While we think of both Congress and the presidency as national offices, the reality is that congressional elections are sometimes more like local elections. Voters may reflect on their preferences for national policy when deciding whom to send to the Senate or the House of Representatives, but they are very likely to view national policy in the context of its effects on their area, their family, or themselves, not based on what is happening to the country as a whole. For example, while many voters want to reduce the federal budget, those over sixty-five are particularly concerned that no cuts to the Medicare program be made.

If they hope to keep their jobs, elected officials must thus be sensitive to preferences in their home constituencies as well as the preferences of their national party.

Finally, it sometimes happens that over a series of elections, parties may be unable or unwilling to adapt their positions to broader socio-demographic or economic forces. Parties need to be aware when society changes. If leaders refuse to recognize that public opinion has changed, the party is unlikely to win in the next election. For example, people who describe themselves as evangelical Christians are an important Republican constituency; they are also strongly opposed to abortion.

Thus, even though the majority of U.S. adults believe abortion should be legal in at least some instances, such as when a pregnancy is the result of rape or incest, or threatens the life of the mother, the position of many Republican presidential candidates in 2016 was to oppose abortion in all cases.

Similarly (or simultaneously), groups that have felt that the party has served their causes in the past may decide to look elsewhere if they feel their needs are no longer being met. Either way, the party system will be upended as a result of a
party realignment , or a shifting of party allegiances within the electorate (
[link] ).